This invention relates to load pallets fabricated with lumber components including stringers and cross deckboards, of the type commonly used in material handling and storage applications. More particularly, the invention relates to the dismantling (or disassembly) of used pallets to provide lumber for the fabrication of new pallets having different dimensions; and especially to an apparatus for cutting through the interface between the stringers and the deckboards so as to separate the components into separate lengths of lumber.
Load bearing pallets for use in supporting various articles and materials, for transport and storage, are generally fabricated by nailing cross deckboards to both sides of two or more generally parallel stringers spaced from one another. The stringers are commonly lengths of 2.times.4 lumber and define interior open-ended spaces. These spaces are adapted to receive for example, the lift arms of a fork lift truck. This permits the article or material secured to the pallet to be lifted and carried by the fork lift truck and to be stored in a convenient manner. Once the article or material has been removed from the pallet, the pallet is generally no longer usable and is often merely stacked for disposal. It is usually the obligation of the pallet fabricator to retrieve the pallet since there is no convenient way for the property owner at the pallet's final destination to dispose of it.
Since pallets are initially fabricated in a great many different dimensions and configurations, it is unlikely that the pallet fabricator can reuse the pallet in its original form. Also, pallets often have broken or damaged cross deckboards after the article or material secured thereto is removed.
For these reasons and others, it is common practice for the pallet fabricator to dismantle used pallets and to use the resulting lumber to fabricate new pallets of different dimensions and configurations. In order to do this, rather than pull the nails, it is much easier to cut through the interface between the cross deckboards and the stringers (and thus through the nails) to separate the cross deckboards from the stringers.
Prior art machines for this operation have frequently used rotary cutting blades such as shown and described in U.S. Pat. Nos. 3,869,780; 4,241,495; 4,346,506; 4,392,403; 4,586,235; 4,750,255; 4,945,626; 5,105,526; 5,205,197; 5,211,094; 5,243,751 and 5,323,525. These machines require several passes of the pallet past the cutting wheels and this makes the process time consuming and costly.
A better approach is to use a band saw with a horizontal cutting span adapted to engage a pallet at the interface between the stringers and cross deckboards along the entire length of the cross deckboards. This type of machine is shown in U.S. Pat. No. 5,201,110. As the pallet is fed toward the blade, all of the cross deckboards on one side of the pallet may be removed in one pass. The partially dismantled pallet may then be flipped over and passed through the blade again to remove the cross deckboards on the other side and thus complete the dismantling process.
Prior art machines, however, require careful, vertical adjustment of either the band saw cutting span or of the table height in order to accurately position the cutting span at the interface between the stringers and the cross deckboards prior to each pass. This adjustment must usually be made for each individual pallet since the thickness of the cross deckboard varies from one pallet to another. This requirement seriously limits the production capability of the machine.
Another problem encountered is that of sorting and removing the lengths of lumber from the work surface once the dismantling is completed. This process delays the feeding of another pallet into the band saw blade.
A further problem is that the operator at the input end must often support the weight of the pallet as it is fed into the band saw cutting span. This can create serious fatigue over a period of time.
Still another problem is that of flipping a partially dismantled pallet over for the second pass through the band saw blade. Here again, the time and effort required limits the speed with which the dismantling task can be completed.
Also, in some instances, a pass through the band saw blade must be halted or interrupted part way through the process and the pallet retracted. Then the pallet must be spun around and restarted through the band saw blade beginning with the opposite end. Here again, the need to spin the pallet around and restart the pass causes operator fatigue over a period of time.
The machine of the present invention reduces the difficulties described above and affords other features and advantages heretofore not obtainable.